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    <script>
        const arr = ["aaa", "bbb", "ccc"];
        function cycle() {
            return arr.reduce(function (prev, next) {
                console.log("prev:", prev);
                console.log("next:", next);
                return prev;     //==>>把初始值保存下来，否则下一个循环没有初始值
            });
        }
        cycle();

    </script>
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